1. Field of the Invention:
This invention is in the field of those devices heretofore provided for vibrating railway cars to effect the unloading of ladings which may be compacted during transit, in the case of bulk ladings, or frozen as with coal, or wet ladings.
2. Description of the Prior Art:
Prior devices in this field have involved metal-to-metal contact between a vibrator mechanism and a railway car which have been utilized as a shake-out to discharge lading through bottom outlets. Such arrangements not only were extremely noisy and detrimental to the environment in this respect, necessitating workmen to wear ear protection in the vicinity of the operation, but in the case of such devices mounted on top of a hopper car for instance, which necessitated use of a crane, the pounding action on the car was so severe as to cause excessive damage to the car.
In the case of a riveted car structure observers have seen the rivets loosen and shake visibly and where bolts were involved the nuts were seen to practically spin off the bolt during the vibration. Some devices immediately preceding the development of this invention utilized non-metallic means between the vibrating structure and the car side wall but in actual practice the non-metallic means, while it reduced the noise level substantially, was unable to stand the various forces involved and due to the friction and heat developed during operation was incapable of functioning for more than a very brief period.
The non-metallic parts were found to last hardly more than a minute when they would begin to smoke and burn and ultimately were completely consumed. These elements were made of rubber strips and where they were pressed against the side of a car they became very hot at the point of contact and the more the rubber burned the higher the noise level became and of course, the unit became less effective in discharging the lading.
Various alternates to the rubber strips were tried in an effort to correct the problem-different grades of rubber were tried, nylon corded strips were tested and even wooden beams 4".times.4" were tried, but all without success and without solving the problem of the short life cycle of the non-metallic elements. At no time was it recognized that the natural frequencies of the vibrating structure relative to the driving motor speed may have been a contributing factor to the problem.